Magnapinna pacificaVecchione and Young, 1998

Pacific bigfin squid

Introduction

Magnapinna pacifica, the type species of the family, was originally described from three individuals (two juveniles about 50 mm ML and a paralarva of 19 mm ML) from the North Pacific. Recently a fourth specimen has been captured from the Gulf of Mexico, Atlantic Ocean. A brief description of the latter specimen can be seen here.

Brief diagnosis:

A Magnapinna with ...

proximal-tentacles wider than adjacent arms.

numerous suckers on proximal-tentacles.

Characteristics

Arms.

Proximal-arm suckers biserial at base, in 3 to 4 series distally.

Distal-arms vermiform.

Inner sucker rings probably smooth.

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Figure. Arms of M. pacifica, holotype, 51 mm ML. Left -Ventral and dorsal views of head and brachial crown. Right - Oral views of distal region of proximal-arms. A - Arm II. B - Arm III. Drawings from Vecchione and Young (1998).

Tentacles.

Proximal-tentacles short, thicker than adjacent arms.

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Figure. Ventrolateral view of the brachial crown of M. pacifica, holotype, showing the large size of the proximal-tentacle relative to arm IV. Photograph by R. Young.

Proximal-tentacle suckers small, in approximately eight series except near base.

Basal one or two tentacle suckers enlarged relative to following suckers.

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Figure. Left - Oral view of the brachial crown of M. pacifica, holotype, showing sucker arrangement on proximal portion of the proximal-tentacles. Note the enlarged suckers at the tentacle base. Right - Oral view of the distal region of the proximal-tentacle of the holotype. Photographs by M. Vecchione.

Figure. Dorsolateral view of the head and brachial crown of M. pacifica, Berry specimen. This specimen had dried out and has been reconstituted. Note the large, broad tentacles and the elongate filaments of the arms which bear suckers in this, presumably, older individual.

Head

Large eyes occupy most of head.

Funnel

Funnel locking-apparatus with oval depression.

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Figure. Funnel locking-apparatus of M. pacifica, holotype. Arrow points to funnel lock, insert shows drawing of the same lock. Drawing from Vecchione and Young (1998). Photograph by R. Young.

Fins

Fins very large: Length equal to or greater than squid length from posterior tip of muscular mantle to tip of tentacles.

Fins terminal.

Width approximates length.

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Figure. Ventral view of M. pacifica, Berry specimen, 49 mm ML (USNM 885787). Photograph from Vecchione and Young (1998) which was found in the archives of S. S. Berry.

Photophores

Photophores absent.

Measurements, mm

Holotype

Berry specimen

Atlantic specimen

Mantle length

51

49

51

Muscular mantle length

16

17

18

Gladius length*

53

52

52*

Fin length

39

40

47

Fin width

34

41

38

Head length

5

4

4

Head width

7

5

6

Eye diameter

4

3

4

Arm I, left/right, to terminal sucker

2.3 / 2.4

-

- / 3.4

Arm II, left/right, to terminal sucker

3.9 / 3.5

-

4.1 / 3.8

Arm III, left/right, to terminal sucker

2.9 / 2.7

-

- / 3.8

Arm IV, left/right, to terminal sucker

4.8 / 4.8

-

- / 3.8

Tentacle, left/right, to terminal sucker

7.1 / 7.4

-

7.4 / 7.0

Arm I, left/right, terminal filament length

2+ / 1.3+

-

-

Arm II, left/right, terminal filament length

2+ / 2.6

-

-

Arm III, left/right, terminal filament length

2.6+ / 2.9

-

-

Arm IV, left/right, terminal filament length

2.0 / 1.3+

-

-

Tentacle, left/right, terminal filament length

2.2 / -

-

-

Comments

M. pacifica is very different from M. atlantica and its close relatives. (1) M. pacifica has much broader proximal- tentacles than proximal-arms while the M. atlantica group of species has much narrower proximal-tentacles than proximal-arms. (2) M. pacifica has proximal-tentacles that are covered with numerous suckers while the M. atlantica group has proximal-tentacles that carry only a few or no suckers. (3) M. pacifica has proximal-arm suckers in three or four series distally while the M. atlantica group has proximal-arm suckers in two series. (4) M. pacifica, unlike M. atlantica but not other members of the group, lacks glandular regions on their proximal-tentacles.

Life History

Only a single paralarva is known. It has the following characteristics:

Arms

Arms short, with suckers in 3-4 series at bases of arms III and IV; otherwise in two series.

Arm tips bare and attenuate.

Tentacles

Tentacles short, broad.

Suckers in 7-8 series distally, grades into buds.

Fins

Muscular mantle overlaps anterior of fins by 15% of fin length.

Fins extend onto a tail posteriorly.

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Figure. Paralarvae of M. pacifica. Left - Ventral and dorsal views, 19.1 mm ML, Hawaiian waters. Middle -
Dorsal view of head of same paralarva. Right - Tentacle of same paralarva. Drawings from Vecchione and Young (1998), modified.

Distribution

The holotype was taken off the California coast at a depth between 0 and 200m in a Bongo plankton net. The other juvenile was found in the stomach of the lancet fish Alepisaurus ferox and the paralarva was taken off Hawaii at a depth between 0 and 300 m in a 4 m2 plankton net. The Atlantic specimen was taken from the Gulf of Mexico in a 3 m2 opening/closing Tucker traw at a depth of 150-300 m over a bottom of 3613 m during 1700-2000 hrs.

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Magnapinna pacificaVecchione and Young, 1998. Pacific bigfin squid.
Authored by
Michael Vecchione and Richard E. Young.
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